Polarization Shaping for Control of Nonlinear Propagation

Abstract

We study the nonlinear optical propagation of two different classes of light beams with space-varying polarization-radially symmetric vector beams and Poincaré beams with lemon and star topologies-in a rubidium vapor cell. Unlike Laguerre-Gauss and other types of beams that quickly experience instabilities, we observe that their propagation is not marked by beam breakup while still exhibiting traits such as nonlinear confinement and self-focusing. Our results suggest that, by tailoring the spatial structure of the polarization, the effects of nonlinear propagation can be effectively controlled. These findings provide a novel approach to transport high-power light beams in nonlinear media with controllable distortions to their spatial structure and polarization properties.

Control of polarization rotation in nonlinear propagation of fully structured light

“…The usual fragmenta-tion of scalar vortex (OAM) beams in Kerr media can be inhibited by using vector vortex or FSL beams. It has been shown that cylindrical vector (CV) beams can additionally propagate with no change to their axially symmetric polarization distribution, while lower order (ℓ = 0, 1) FSL beams experience a polarization rotation [14]. We note that azimuthally polarized, spatial, dark soliton solutions of Maxwell's equations without OAM have been demonstrated in [33].…”

“…Obviously for more exact measurements, the rotation can be measured and compared at many points across the beam. In the simulations reported below, we have selected P 0 = 7.4mW, I sat = 5W cm −2 , n 2 = 8 × 10 −6 cm 2 /W and λ = 780nm that reproduce the experimental configuration given in [14]. We use a beam waist of 100µm throughout (unless explicitly stated otherwise), corresponding to a Rayleigh range of approx.…”

“…Although the effect of beam spreading due to diffraction during linear propagation can be mitigated, and in some cases exactly balanced, by using a self-focusing (Kerr) nonlinear medium, OAM beams are known to fragment into multiple (twice the OAM) soliton peaks during nonlinear propagation [21,22]. It has been shown that this fragmentation can be inhibited, without altering the nonlinear confinement, by using vector beams instead of scalar beams [14,[23][24][25]. Indeed, it has been shown that cylindrical vector (CV) beams can propagate in a saturating Kerr nonlinear medium with no change to their spatial profile or their axially symmetric polarization distribution for much longer distances than the equivalent scalar beams [14].…”

“…It has been shown that this fragmentation can be inhibited, without altering the nonlinear confinement, by using vector beams instead of scalar beams [14,[23][24][25]. Indeed, it has been shown that cylindrical vector (CV) beams can propagate in a saturating Kerr nonlinear medium with no change to their spatial profile or their axially symmetric polarization distribution for much longer distances than the equivalent scalar beams [14]. Similar spatial confinement can be seen for FSL beams, though in this case the nonlinear propagation will affect the rotation of the polarization structure.…”

“…The resultant beam has non-uniform spatial intensity, phase and polarization distributions. The ability to control both the spatial intensity and the polarization distribution of the optical field is of use in material processing [4]), in STED and confocal microscopy [5][6][7][8], in optical trapping and manipulation [9,10], in atomic state preparation, manipulation, and detection [9,11,12], in optical communications [13,14] and even classical entanglement [15][16][17]. Additionally, novel focussing properties associated with particular polarization distributions can lead to tighter focussing [18] and strong axial field components that are of use in microscopy [5,6], optical trapping [9], and as a mechanism for linear accelerators [19].…”